The overall objective of my proposed research is to determine which genetic factors are involved in the expression and suppression of malignancy in human cells and to identify the specific chromosome(s) involved. The techniques in these studies include somatic cell hybridization of malignant and normal cells and isolation of the resultant hybrid. These hybrids will then be tested in immunosuppressed mice for their oncogenic potential. Preliminary evidence indicates that malignancy behaves as a recessive trait and is suppressed when genetic material from a normal cell is present. We intend cloning our hybrid populations to isolate malignant revertants and identify by chromosomal analysis (utilizing banding techniques) the chromosome(s) which have been segregated, allowing for re-expression of malignancy. The project outlined above should significantly contribute toward the problem of resolving the possibility that malignancy is related to a cellular regulatory factor. In addition to resolving the question of dominance or recessiveness of malignancy in human cells, several other important questions relating to differences between malignant and normal cells can be investigated.